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Ozone hole healing may increase climate warming | In a surprising new research, scientists have said that although the hole in the ozone layer is now steadily closing, but its repair could actually increase warming in the southern hemisphere. The Antarctic ozone hole was once regarded as one of the biggest environmental
threats, but the discovery of a previously undiscovered feedback shows that it
has instead helped to shield this region from carbon-induced warming over the
past two decades. High-speed winds in the area beneath the hole have led to the
formation of brighter summertime clouds, which reflect more of the sun's powerful
rays. "These clouds have acted like a mirror to the sun's rays, reflecting the
sun's heat away from the surface to the extent that warming from rising carbon
emissions has effectively been cancelled out in this region during the summertime,"
said Professor Ken Carslaw of the University of Leeds who co-authored the research.
"If, as seems likely, these winds die down, rising CO2 emissions could then cause
the warming of the southern hemisphere to accelerate, which would have an impact
on future climate predictions," he added. The key to this newly-discovered feedback
is aerosol - tiny reflective particles suspended within the air that are known
by experts to have a huge impact on climate. Greenhouses gases absorb infrared
radiation from the Earth and release it back into the atmosphere as heat, causing
the planet to warm up over time. Aerosol works against this by reflecting heat
from the sun back into space, cooling the planet as it does so. Beneath the Antarctic
ozone hole, high-speed winds whip up large amounts of sea spray, which contains
millions of tiny salt particles. This spray then forms droplets and eventually
clouds, and the increased spray over the last two decades has made these clouds
brighter and more reflective. As the ozone layer recovers it is believed that
this feedback mechanism could decline in effectiveness, or even be reversed, leading
to accelerated warming in the southern hemisphere. "Our research highlights the
value of today's state-of- the-art models and long-term datasets that enable such
unexpected and complex climate feedbacks to be detected and accounted for in our
future predictions," said Professor Carslaw. |
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